Projectile control system



July 7, 1953 L. ATZ 2,644,397

PROJECTILE CONTROL SYSTEM Filed Jan. 6. 1945 f /if y BY Patented July 7, 1953 UNITED STATES OFFICE TENT (Gramted. under Title ;.U. S. Cbde (1952)', sec. 2665 8 Claims.

Theainvention described herein may be manufactureclandusedby or for the Government for governmental i purposes; o without theY payment to meof anyvroyalty thereon.

This invention relates to self-guidedprojectiles and; morezparticularlyto projectiles that. operate inresponse to sonic wavesfthat areemitted by a target'.V

Numerous systems` have been proposed heretofore for: the" automatic guidance of projectiles such asitorpedoes.;that.are self-propelled toward atarget; andithe'like. Such systems usually comprise projectiles. incorporating steering control means incooperationwith direction finders which spottheftargetland'infiuence the control means in a manner and to` a degree that arenecessary to bringitlieprojectile in lines-With the target. The nature: ofrthe direction finder is such that it reacts to a` distinctive" formi` of: energyy emanated' by the targettowardiwhich the projectile is: directed.

Directionzfindersare in` generalresponsive toa featureiwhich is unique `infaitarget"1 otherwise vthe projectilemight' be ledtoan unintended destination. When the: target is a power driven vessel, aircraft, flying bombior the like, thedistinguishablel'feature Whichflends :itself most effectively for direction: finding purposes isY the'4 sound emanating' from the target and.: propagated in air or through".water.` inasmuch as sounds generated by aircraft or vessels are of a high order of intensity, their.' detection and location are feasible from'.remotelocations;

The objects oft? the present invention comprise the provision off, a self-propelled. projectile that contains a direction finder for determining the positicnzof va `sourceofsonic' radiation.; afprojectile containing'a direction finder which" functionsiin cooperation with steering control means to direct thefprojectile t'o al sound'emittingtarget; and'a projectile: containing a safety means that' funce tions inconjunctioniwith the automatically directed projectile 'for 'renderingfthe directionLi-lnder inoperative in: the. presence: of4 a sound emitting target that isffriendiy;

With theabove'fandiother obj ectsin1view "which willb'e .apparent to lthose who areinformed in .the iiel'clflof. air borne equipment from the following description, an` illustrative embodiment of the present" invention is shownY in the' accompanying drawing, wherein-z Fig. 1 isla perspective'view of an-aerialltorpedo that embodies' the-present invention; and

Fig; 2 is a` block diagram of a circuit arrangement that forms a part of the present*` invention asiapplied to lthe torpedo-that'. isrshowni in Fig; 1.

A power driven vessel, aircraft or flying bomb ingeneralogenerates a spectrum of sonic waves of diverse.. frequencies, of which. certain specific frequencies arepredominant. In the orientation of the. projectile'device thatforms a part of the presentinvention, a small region of thisspectrum is utilized with the result that theincomingwave after passing through a lter can be substantially treated as a-` sine wave.

In intercepting. sound. wavesit must be `borne in mindthatfthese waves areof a longitudinal nature and that. the wavefront emanatingfrom a sound source'is. substantially a sphere. If the sound source isiixed with respect to the transmission medium. andanobser-vation post,.the apparent frequency. will-remain the same no matter. how far the wave travels. AtV the observation post the wave front lmaybe viewedas aplane perpendicular to thedirection of itsmotion; It will be evident that if a-pairof: observation posts are both intercepting a sound wave from a given source, the observation-posts will both receive the same frequency, irrespective of differences in their distances from the. source of sound; If two observation postszlie inplanes that are spaced from each other andthat are.A both parallel to a wave front travellingfrom'asound source of a` given frequency, and the spaced planes are less than a wavelengthofthat frequency apart, a soundpressure differential.orphasediference will exist between the. two observationposts as a function of the spacing between their respective planes.` This phase diiierencewillibezero when the observation posts lie in. the` same planeu and will be 360 when the planes. are a wavelength apart,

This phenomenon aordsthe basis for the present inventionandisutilizedby fitting a projectile with foursound detectors, each arrangedat 99 pointsialongthe circumference of acircle concentric'with the longitudinal axis. of theA projectile and lyingr inA a plane perpendicular thereto. The diameter of the circle is less than a half wavelength long fora given sound frequency that is emitted by the source of the soundoi` the` objective'for whichtheprojectile is intended. Two detectors at opposite ends of a common diameter are associated with the steering control of the projectile governing" the angular orientation of the projectile` inA flight in a first or azimuthal plane,.whereassthe other two detectors at to therstpair of4 detectors are associated with the steeringz control: means of tlieprojectile governing; the"angularorientation thereof in an elevationalnplane.normallyvdisposed to said first plane.

`Wfhenvthe: detectors are;- oriented with respect to the sound emitting source so that their outputs are in phase, the steering controls are maintained at a center or null point. When one detector is advanced in phase with respect to the other, the associated steering control is operated to left or right, upor down, as required to effect a correc-I tion in the course of the projectile, bringing it into line with the sound-emitting target.

A projectile in the form of an anti-aircraft torpedo that is propelled and steered by the forces of reaction that originate with the spontaneous combustion of gases which are ejected at high speed from the tail of the torpedo is illustrated in Fig. 1 of the accompanying drawing. Although the invention will be described in connection with a projectile of the aforementioned type for purposes of illustration, it is not intended to be limited thereto and may be adapted to function in an equally effective manner with other types f projectiles. The combustible gases preferably are separately maintained under pressure in tanks housed within the projectile in commonly known manner, and, after ring in a mixing chamber, are ejected through an exhaust nozzle I9 opening outwardly from the rear of the projectile and substantially axially thereof to propel the projectile straight ahead on a continuous course.

Four projectile supporting wings II, I2, I3 and I4, extend radially from and preferably are integral with and extend longitudinally of the body 9 of the torpedo. Adjacent wings are substantially perpendicular with respect to each other. A corresponding number of sound detecting devices such as the microphones I8, I'|, I 6, and I5, or other suitable type of electrical detector that is responsive to sonic impulses, are individually mounted at radially equidistant points radially outwardly of the leading edges of the wings II,

l2, I3 and I4, respectively. The projectile is provided with tail fins I9, 20, 2|, and 22 that preferably are coplanar with the wings I4, I3, I2 and i I respectively and that provide rudder and elevator surfaces for maintaining a flight course that is normally continuous straight ahead and level where the four microphones I5, i6, I'| and 8 receive the same sound impulse at the same time. The torpedo is steered by the ejection of gases from nozzles 23, 24, 25, and 26 that open selectively thru one side of the faces of the ns 20, 2 l, I9 and 22 respectively and correspondingly disposed nozzles, not shown, that open oppositely thereto. These steering nozzles 23, 24, 25, and 25 and the corresponding nozzles on the opposite sides of the fins 2B, 2|, I9, and 22 eject gases in streams, the axes of which are perpendicular to the direction in which propelling gas is ejected from the nozzle I0. The course that is assumed by the projectile is the resultant of the forces of reaction that are created by the discharge of gases that are ejected thru the main driving jet from the nozzle vI!! and from the jets in the ns IS, 20,2Ia11d 22.

A charge that is disposed within the body 9 of the torpedo explodes when the nose 39 thereof impinges upon a target. Electrically operated valves, not shown, are provided in the pipe lines on the steering jets 23', 24, 25, and 26, and the jets that are opposite thereto, .for individually controlling the gas now in the jets, thereby controlling the direction of flight of the projectile in azimuth and in elevation. Each microphone I 5, I S, I l' and I8, is associated thru valve controls with its particular jet valve in a n correspondingly positioned relative to the wing carrying the particular microphone.

The distances between the pair of microphones I5 and Il, and the pair of microphones IG and I3 are less than a half wavelength for a given frequency and are well within the range of the sound emitted by the target and passed by the filters 4|) and 13| of Fig. 2. When the longitudinal axis of the torpedo is coincident with a line from the projectile to the source of sound, all of the microphones I5, I6, I and I 8, lie in a plane that is parallel to the assumed plane of the wave front. Where the torpedo axis is not aligned with the radial line emanating from the sound source, the microphone currents will be out of phase to a degree that is contingent upon the extent of the deviation. The microphone I6 controls the gas jets from the nozzles 2d and 25 in the vertical fins 2| and I9, respectively, to thrust the tail of the projectile in one lateral direction, and the microphone I8 controls gas Vjets from corresponding nozzles, not shown, on

the opposite side of the vertical fins 2| and I9 to thrust the tail of the projectile in the opposite lateral direction.

If the projectile is approaching a wave front that is not normal to'the axis o-f the projectile body portion 9 and the microphone I6 is incident to the wave front before the microphone I8 is incident thereto, then the nozzles 24 and 25 are caused to emit gas jets to veer the projectile so that the axis of the projectile body portion 9 becomes normal to the plane of the sound wave and until both microphone It and I8 receive sound waves which are in phase, Whereupon the pair of gas jets is cut off.

In a similar manner, if the microphone I8 strikes the wave front before the microphone I6 does, then gas jets are started from the pair of nozzles, not shown, on the sides of the fins 2| and I9 that are opposite to the sides carrying the nozzles 2d and 25, respectively, so that the nose 39 of the projectile is turned toward the source of sound, or the axis of the body portion 9 is directed toward a normal position with respect to `the plane of the sound wave. The ejected gas compels the torpedo to shift position until both microphones receive sound Waves which are in phase resulting in the laterally directing jets being cut off.

The microphones I5 and cooperate in a similar manner to cause the projectile to either climb or dive by emitting gas from the nozzles 23 and 26 or from the nozzles opposite thereto, not shown, respectively. The action of the valves controlling the various gas jets in the projectile fins I 9, 2|), 2| and 22 is positive and will open when there is any phase difference existing between the microphones I5, I 6, I'I, and I8, irrespective of the degree of such phase difference. Thus, by the combined functioning of the radio channels from the microphones I5, I6, Il, and I8, the torpedo is brought into line with and is maintained on a course straight to the target.

The microphones it and IB open into individual electric energy conducting channels, as

I6 and I8 convert the sound waves that are intercepted thereby, are` passed from the microphones I6 and I8 to the pretuned'f'llters 46 and 4I, respectively, that are shown in Fig. 2 and that function in the usual manner to clarify the audio signals and to resolve them into preferably sine waves such as those shown above the lter land below the lter 4|. The filters 48 and 4I pass their respective audio signals to amplifiers 2`I and 3|, respectively. Each microphone I5 to I8 inclusive, is associated with a correspondingly positioned jet, through an amplifier which under certain conditions operates an electrical valve when a sound is interceptedl by the microphone. The amplifying channels of the microphones V[second ranged in a manner whereby themicrophone nearer the source of sound, opensits associated nozzle and simultaneously causes the other microphone channel to be inoperative.

A preferred block diagram circuit for control-V ling the operation of the' getjets that are emitted from the fins I9, 20, 2| and'22 from. the microphones i5, I6, I'I, and I8, is shown 2 of the accompanying drawing. "lhecfircuit` arrangements for the microphones I6 and I8 are shown in block form. The microphones I5 and I'I are associated with a substantially duplicate circuit and hence need not be shown. The out;- put of the microphone I6 is impressed upon the input circuit of the vacuum, tube amplifier 21 after having been fed through the pretuned filter 4|). l 1

The output of the microphone I8 is Aimpresse thru the lter 4| upon the amplifier 3|.

The filters 49 and 4I aredesigned toselect a single harmonic of the sound emanating from the target so that their outputs are substantially sine waves of a common frequency.

The outputs of the amplifiers 21' and 3|, as ilf lustrated above the amplifier `2'I and below the amplifier 3|, are applied to square wave circuits 28land 32 which level olii' the tcp portion of the sine waves so that the waves assume substantially the form of square waves, as shown above the square wave circuit 28, and `below the square wave circuit 32. This may be accomplished by conventional limiter circuits that employ vacuum tubes operating in the saturation portion of the plate characteristic curves. Although the initial sound wave may not be of puresinusoidal form, this factor is of no importance because of the action of the filters 4D and 4I.. The negative going portions of the square wave output of the squarewave circuits 28 and 32 are removedrby y, half wave rectiers 29` and 33,' `as shownthereabove and therebelow, respectively.` The output of the rectiers 29 and 33 are fed to coupling circuits 30 and 34respectively;

The output of microphone I8, as shown below amplifier 3|, in `a similar manner, is Aamplified after having gone through a filter 4I. It is then converted into a square Wave pulse by the amplifier 3| and the squarewave circuit 32. The half wave rectifier 33 removes the negative going portion of the Wave as indicated below the rectifier -33 in the block diagram. The output of rectier 33 is applied to a coupling circuit 3,4 that is substantially a duplicate of coupling circuit 39.

The individual coupling circuits 3|)` and 34 comprise a vacuum tube amplifier, not shown. The amplifiers in the coupling circuits 3|] and 34 are mutually connected by connectors 42 l and 43 in such a manner that the plate of the amplier in the coupling circuit 38 is connected I3 are cooperatively arthrough suitable` circuit elements to the grid of theamplilier in the coupling circuit 34 and vice versa with thistrggering arrangement, the rst coupling circuit to receive a square wave pulse from its associated rectier 29 or 33 generating a biasing voltage which blocks-the other coupling circuit for a limited period. The period extending-beyond the application of the pulse, commencing` withthe application of one square Wave pulse,v lasts until shortly before the appearance of the next ,square wave pulse. This result is accomplished by initially biasing each coupling circuit 30 and 34 almost to the point of cut-off and associating theloutput of each coupling circuit With-the biasing circuit of the other, so that the first coupling circuit 30 or 34 to receive a square wave pulse in the input circuit thereof imposes a bias upon. the other coupling circuit to a point greatly below cut-off. The incoming square wave pulse vthat is fed to the more heavily cut-off biased-couplingcircuit is unable to overcome this bias as long-as it is imposed. The out-off bias is maintained for a period that extends beyond the duration of the square wave pulso by any suitable known Storing network, such as a resistancecapacitance network or the like. It should be noted that this` operation will only be consiste-nt when the phase difference is smaller than In general this steering control is intended to correct` the projectiles course after it has been launched in the direction of the target. The outmit` of the coupling circuit 30 is fed to a valve control circuit 35, preferably in the form of a conventional electronic'relay which opens the particular nozzle valves 2-4 and 25 that are associatedvlwith the microphone I6, as long'as the coupling circuit 3|)l is operative. The output of the coupling circuit 34 in a like manner is associated with a valve control circuit 3.6 that operates the valves of the nozzles that are associated with the` microphone I8 and that are disposed on the sides of the fins I9 and 2| that are opposite to the sides thereof upon which the nozzles 24 and 25 are disposed.

When the projectile is oriented on a line with the target, both microphones I6 and I8 are caused to generate in-phase currents that cause the coupling circuits 39 and 34 to be rendered inoperative and to return the valve control circuits 35 and 36 to their normally closed condition. While the projectile is so oriented its course remains unchanged. If, however, the phase of the current that is generated in the microphone I6 is advanced by a small amount with respect to that `of the microphone I8 because of the angular orientation of the torpedo from the target line, the pair of nozzles 24 and 25 that are associated with` the microphone I6 will be actuated, thereby causing the torpedo to swerve to a position in line with the target.` When this occurs the currents of the microphones I6 and I8 are again in phase and neither valve control circuit 35 or 36 is operated.

The microphones I5 and I1 operate in association with their respective set of nozzles in substantially the same manner in which the microphones I6 and I8 operate but in a plane perpendicular thereto. This association provides for the angular correction of the night path of the projectile both in elevation and in azimuth, and maintains the night course of the torpedo directly toward the target.

A 'safety device for inactivating the torpedo control in the presence of a friendly plane is provided by inserting a peaked filter network in the outputs of the microphones I6 and I8 in known manner. VThe friendly plane is provided with a sound generator whose frequency is equal to the resonant frequency of the peaked filter 31, so that when the microphones I6 and I8 interceptthis signal, the currents that are generated in the microphones are passed through the peaked nlter 31 and are fed Ato an amplifier biasing circuit 38 .which serves to impress a cut-olf bias on the amplifiers 27 and 3|, thereby rendering both microphone channels inoperative. The filter 3l discriminates against all frequencies other than the 'frequency of the friendly sound generator and since the safety circuit is operated only by the sound generator on a friendly plane. The frequency of the friendly sound generator preferably lis chosen to be below that ordinarily'initiated'in air by plane propellers.

The distance between the microphones I5 and I'I and the distance between the microphones IB and I8 are preferably equal and are chosen so that they are less than one quarter of the frequency passed by filters 4I) and 4 I. The Doppler effect which causes the apparent frequency to change if the relative velocity between target and torpedo changes will be small if the torpedo is launched in the general direction in which the target is travelling. The torpedo will normally describe a follower curveff The Doppler effect will be minimized as long as the angle between the direction of flight of the target and the direction of flight of the torpedo remains smaller than 90.

It is to be understood that the self-propelled projectile and the circuit therefor that have been shown and described herein have been submitted for the purposes of illustrating and explaining one embodiment of the present invention and that various modifications and improvements may be .made therein Without departing from the scope of the present invention, as defined by the appended claims.

What -I claim is: I

1. A projectile of the character described, comprising a body' portion,'four wings radiating Yfrom and adjacent thelead end of said body 'portion and coplanar with each other in pairs,

ence control means operating said gasv jet` emitting means from said sound detectors, and means for blocking the operation of said phase difference controlmeans upon reception of a predetermined signalbyv said sound detectors.

2. A projectile of the character described, comprising a body portion, four Wings radiating vfrom and adjacent the lead end of said body portion and coplanar with each other in pairs, sound detectors in the lead edges of coplanar pairs of said wings, four fins adjacent the trailing end of said body portion and each of said fins being substantially coplanar respectively with one of said wings, gas vjet emitting means forming a part of each of said fins for directing the flight course of the projectile, means responsive to phasedifference between'signalsfrom a first pair of said sound detectors for effecting from said `fins a steering operation in a direction bringing 4said signals-into phase coincidence, means responsive to phase diiference between signals in a second pair of detectors-for effecting a steering operation in a direction bringing the signals into phase coincidence, and means blocking the steering operation upon the reception of predetermined signal at said sound detectors.

3. A projectile of the character described, comprising a body portion, a plurality of wings arranged in coplanar pairs and radiating from and adjacent to the lead end of said body portion, detector means in the lead edges of each of said Wings, an equal plurality of fins adjacent to the trailing end of said body portion, each of said fins being coplanar, respectively, with one of said wings, jet means `forming a part of ea-ch of said fins for directing the flight course of the projectile, means responsive to phase difference between signals from" a first pair of said detector means for effectingA from said fins a steering op-V eration in a direction bringing said signals into phase coincidence, means responsive to phase difference between signals in a second pair of detector means for effecting a steering operation in a direction bringing thesignals into phase coincidence, and means blocking the steering operation upon the receptionv vof a predetermined signal at said. detector means. 4. A projectile ofthe character described, comprising a body portion, a plurality of wings arranged in coplanar pairs at one end 0f said body portion, sound detector means in `the lead edges of each of said wings, an equal pluralityof ns at Ythe other end'of said body portion, each of said fins being coplanar, respectively, with one of said wings, jet means forming a part of each of said fins for directing the flight course of said projectile, a plurality 'of channels, each responsive to a given frequency Tand each respectively connected to the output from one of said detector means, for activating said jet means in response to the output of said detector means, means interconnecting each pair of said channels respectively associated with each ofsaid coplanar pairs of Wings, one of each of said pairs of channels serving toremove its associated channel from the circuit in response to a phase difference in the input to said detector means so as to effect a steering operation of said projectile which will bring said input into each of said pairs of detector means into phase coincidence.

5. The projectile of claim 4, further includingr means for blocking the operation of all of said channels uponthev reception of a predetermined signal frequency at said detector means.

. 6. A projectile of the character described, comprisinga body portion, a plurality of Wings arranged in kcoplanar pairs at one end of said body portion, sound detector means in the lead edges of each'of said Wings, an equal plurality of ns at the other end of said body portion, each of said fins beingv coplanar, respectively, with one of said Wings, jet means forming a part of each of said ns for directing the flight course of said projectile, a plurality of channels, eachres'ponsive to a given frequency and each respectively 'connected to ther-output from one of said detector means, for' activating said jet means in response to the output of said detector means, each of said channels respectively comprising filter means connected to thevoutput of said detector means and means connected to the output of said filter means and responsive thereto for activating the corresponding jet means, each pair of said lastnamed means, associated with each of said coplanar pairs of wings, being coupled together in order that a phase difference in the output of said detector means will deactivate the channel associated with the lagging signal so as to effect a steering operation of said projectile and bring the outputs of each pair of said detector means into phase coincidence, and means adapted to become operative upon the reception of a predetermined signal frequency at said detector means and coupled to all of said channels for blocking the operation thereof.

7. In a directional system including at least two channels for receiving wave energy generated by a moving source, wherein the phase of the received energy in one of said channels differs with respect to the phase of received energy in the other of said channels due to the direction of reception of said energy: means in each of said channels for squaring said Wave energy, means interconnecting said channels for enabling the first one of said channels receiving said energy to deactivate the other of said channels in response t and for at least the duration of each square wave in said first channel, and utilization means connected to the square wave outputs of said channels and responsive thereto.

8. In a directional system including at least two channels for receiving wave energy generated by a moving source, wherein the phase of the received energy in one of said channels differs with respect to the phase of the received energy in the other of said channels due to the direction of reception of said energy by said channel: means in each of said channels for squaring said Wave energy, means interconnecting said channels for enabling the rst one of said channels receiving said energy to deactivate the other of said channels in response to and for at least the duration of each square Wave in said rst channel, utilization means connected to the square wave outputs of said channels and responsive thereto, and means connected to said channels and responsive to energy of a given frequency for completely deactivating all of said channels and preventing any energy from passing therethrough.

LEONHARD KATZ.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,303,105 Murdock May 6, 1919 2,007,211 Nicolson July 9, 1935 2,109,475 Fanning Mar. 1, 1938 2,145,507 Denoix Jan. 3l, 1939 2,165,800 Koch July 11, 1939 2,349,370 Orner May 23, 1944 2,378,939 Nicolson June 26, 1945 FOREIGN PATENTS Number Country Date 441,866 Great Britain Jan. 27, 1936 339,479 Italy Apr. 22, 1936 l 832,427 France July 4, 1938 546,488 Great Britain July 16, 1942 

